Fifteen people were shot, one fatally, at a packed nightclub in Cincinnati, Ohio, early on Sunday, and police said they believed at least two shooters may have been involved.
The motive was still unclear, but Cincinnati Assistant Police Chief Paul Neudigate said on Twitter that "there are no indications this incident is terrorism related."
The shooting took place around 1 a.m. when hundreds of people were reported to be at the Cameo Nightlife club, which the Cincinnati Police Department said has had "multiple problems" in the past.
"At this point it's unclear exactly what instigated the shooting," Captain Kimberly Williams said at a televised briefing. "We believe that there were at least a couple of shooters involved."
"Just a lot of chaos when the shots went off," Williams added.
The suspects were at large and police do not have good descriptions of them, in part because witnesses were reluctant to cooperate, Williams told WCPO.
The shooting comes less than a year after a gunman opened fire at a gay nightclub in Orlando, Florida, killing 49 people. It was the deadliest mass shooting in US history.
Several of the victims in Cincinnati had life-threatening injuries, WLWT-TV reported on its website, quoting Neudigate, who said hundreds of people were in the nightclub at the time of shooting.
"We are in the middle of a very horrific situation that occurred at the nightclub with multiple victims," Neudigate told NBC News.
"It's going to be a long night for our homicide units to investigate this incident, but right now things are stable."
The University of Cincinnati Medical Center admitted eight people early Sunday, a spokeswoman told ABC News, but she did not say specifically whether the patients were connected to the nightclub shooting. A representative of the hospital could not be reached immediately for comment.
The club, a large single-story structure, is a 7-mile (11 km) drive from downtown Cincinnati near the southeast corner of the city, the heart of the second largest metropolitan area in Ohio with more than 2 million residents.